Alpha-olefin polymerization catalyst system which contains an aromatic silane compound

ABSTRACT

Aromatic silane compounds containing at least an aromatic ring bound directly to the silicon atom, wherein the aromatic ring has at least one substituent located in the ortho position selected from C 1-10  hydrocarbon groups, are useful as electron donors in olefin polymerization catalysts for the production of polyolefins having a stereoblock content of from about 7 to about 25%.

BACKGROUND OF THE INVENTION

[0001] This invention relates to aromatic silane compounds and toZiegler-Natta catalyst systems which use said aromatic silane compoundsas electron donors for the production of olefin polymers. The olefinpolymers produced with such catalyst systems exhibit a desirablestereoblock content of from about 7 to about 25%.

[0002] Polymer stereoblock content can affect the physical properties ofthe polymer itself and those of products prepared therefrom,particularly films manufactured from such polyolefins and blends of suchpolyolefins with elastomeric materials, regardless of whether they aremechanically blended from pre-produced polyolefins and elastomericmaterials or reactor blended by first producing such a polyolefin thenproducing the elastomeric material in the presence of the polyolefin.

[0003] Organosilane compounds have been used in catalysts (1) as aninternal electron donor in a solid catalyst component comprising ahalogen-containing titanium compound supported on an activated magnesiumdihalide compound and (2) as an external electron donor in combinationwith an aluminum-alkyl co-catalyst. Typically the organosilane compoundshave Si—OR, Si—OCOR or Si—NR₂ groups, where R is alkyl, alkenyl, aryl,arylalkyl or cycloalkyl having 1 to 20 atoms. Such compounds aredescribed in U.S. Pat. Nos. 4,180,636; 4,242,479; 4,347,160; 4,382,019;4,435,550; 4,442,276; 4,473,660; 4,530,912 and 4,560,671, where they areused as internal electron donors in the solid catalyst component; and inU.S. Pat. Nos. 4,472,524, 4,522,930, 4,560,671, 4,581,342, 4,657,882 andEuropean patent application Nos. 45976 and 45977, where they are used asexternal electron donors with the aluminum-alkyl co-catalyst.

[0004] Conventional propylene homopolymers, obtained by using externalelectron donors known in the state of the art, show a high degree ofcristallinity, which determines the physical properties of the polymers,such as high melting temperature, high glass temperature and highΔH_(fus). These physical properties, while necessary in someapplications, are often disadvantageous in fiber and film applications,where lower bonding temperatures are required, for instance in producinglaminate structures.

[0005] Hence, there is the need for external electron donor compoundswhich allow propylene polymers to be obtained having a relatively highdegree of stereoblocks, at the same time at acceptable polymerizationyields.

SUMMARY OF THE INVENTION

[0006] It has been surprisingly found that a novel class of substitutedaromatic silane compounds can be used as external electron donors forolefin polymerization catalyst systems, in order to produce propylenepolymers having a stereoblock content of from about 7 to about 25%.

[0007] In one aspect, the present invention concerns an aromatic silanecompound useful as electron donor compound in an olefin polymerizationcatalyst, having formula (I):

[0008] wherein

[0009] R₁ is selected from the group consisting of linear or branchedC₁₋₂₆ alkyl, C₂₋₂₆ alkenyl, C₁₋₂₆ alkoxy, C₂₋₂₆ alkoxyalkyl, C₇₋₂₆arylalkyl, C₃₋₂₆ cycloalkyl and C₄₋₂₆ cycloalkoxy groups, optionallycontaining one or more halogen atoms;

[0010] R₂ is an aromatic ring having at least one substituent in theortho position selected from C₁₋₁₀ hydrocarbon groups; and

[0011] R₃ and R₄, the same or different from each other, are selectedfrom the group consisting of a linear or branched C₁₋₁₀ alkyl and C₃₋₁₀cycloalkyl groups.

[0012] In another aspect, the present invention concerns a catalystsystem for the polymerization of olefins comprising:

[0013] (A) an aromatic silane compound having formula (I):

[0014] wherein

[0015] R₁ is selected from the group consisting of linear or branchedC₁₋₂₆ alkyl, C₂₋₂₆ alkenyl, C₁₋₂₆ alkoxy, C₂₋₂₆ alkoxyalkyl, C₇₋₂₆arylalkyl, C₃₋₂₆ cycloalkyl and C₄₋₂₆ cycloalkoxy groups, optionallycontaining one or more halogen atoms;

[0016] R₂ is an aromatic ring having at least one substituent in theortho position; and

[0017] R₃ and R₄, the same or different from each other, are selectedfrom the group consisting of a linear or branched C₁₋₁₀ alkyl and C₃₋₁₀cycloalkyl groups;

[0018] (B) an aluminum alkyl compound; and

[0019] (C) a solid catalyst component comprising Mg, Ti, halogen and anelectron donor compound.

[0020] In another aspect, this invention concerns a process for thepolymerization of alpha-olefins carried out in the presence of thecatalyst system described above, to produce a polyolefin having astereoblock content of from about 7 to about 25%, and preferably from 12to 20%.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The inventors have discovered that organosilanes having anaromatic ring substituted in the ortho position can produce, inconjunction with the catalyst systems described below, polyolefin resinshaving a stereoblock content of from about 7 to about 25%.

[0022] The aromatic silane compounds of the present invention have thefollowing formula (1):

[0023] wherein R₁, R₂, R₃ and R₄ have the meanings reported above.

[0024] In one preferred embodiment of the present invention, R₁ is alinear or branched C₁₋₁₈ alkyl or C₃₋₁₈ cycloalkyl, and even morepreferably R₁ is a linear C₁₋₅ alkyl or a branched C₃₋₈ alkyl.

[0025] R₂ is an aromatic ring having at least one substituent in theortho position selected from C₁₋₁₀ hydrocarbon groups. Depending on thestereoblock content desired, R₂ may preferably be a non-heterocyclicaromatic system, and most preferably a mono-substituted phenyl ringsystem, a di-substituted phenyl ring system, or a mono-substitutednaphthyl ring system. By “substituent in the ortho position”, it ismeant that at least one of the two aromatic ring atoms adjacent to thearomatic ring atom that is bound to the silicon atom must besubstituted.

[0026] The groups R₃ and R₄, the same or different from each other, arepreferably C₁₋₁₀ alkyl, and even more preferably are methyl or ethyl.

[0027] Illustrative examples of aromatic silanes which conform toformula (I) include the following:

[0028] (2-ethylphenyl)-3,3-dimethylbutyl-dimethoxysilane;

[0029] (2-ethylphenyl)-3-methylbutyl-dimethoxysilane;

[0030] (2-ethylphenyl)-propyl-dimethoxysilane;

[0031] (2-ethylphenyl)-3,3,3trifiuoropropyl-dimethoxysilane;

[0032] (2-methylphenyl)-propyl-dimethoxysilane; and

[0033] (2,6-dimethylphenyl)-propyl-dimethoxysilane.

[0034] The aromatic silanes of the present invention may be preparedfrom readily available starting materials using conventional synthesismethods and equipment well known to those of ordinary skill in the art.Aromatic silanes where the aromatic ring system is an ortho-substitutedphenyl group may be prepared by the reaction between the appropriate2-phenylmagnesium bromide and the appropriate alkyktrialkoxysilane, asillustrated in Example 2. Alternatively, such ortho-substituted aromaticsilanes may be prepared by first reacting the appropriate 2-bromobenzenewith an alkyl lithium reagent, such as n-butyl lithium, to generate thecorresponding 2-phenyl lithium, which is then allowed to react with theappropriate alkyl-trialkoxysilane, as illustrated in Example 3.

[0035] The organosilanes of the present invention are useful as theexternal electron donor in an olefin polymerization catalyst system.More particularly, the present invention concerns a catalyst system forthe polymerization of olefins comprising:

[0036] (A) an aromatic silane compound having formula (I):

[0037] wherein

[0038] R₁ is preferably a linear or branched C₁₋₁₈ alkyl or C₃₋₁₈cycloalkyl, and even more preferably R₁ is a linear C₁₋₅ alkyl;

[0039] R₂ is an aromatic ring having at least one substituent in theortho position;

[0040] R₃ and R₄, the same or different from each other, are preferablyC₁₋₁₀ alkyl groups, and even more preferably are methyl or ethyl;

[0041] (B) an aluminum alkyl compound; and

[0042] (C) a solid catalyst component comprising Mg, Ti, halogen and anelectron donor compound as essential elements.

[0043] In said aromatic silane compound (A), R₁ is preferably selectedfrom the group consisting of linear or branched C₁₋₁₈ alkyl, C₁₋₁₈alkoxyl and C₃₋₁₈ cycloalkyl groups, and even more preferably R₁ isselected from the group consisting of linear C₁₋₅ alkyl and branchedC₃₋₈ alkyl groups. R₂ is preferably selected from the group consistingof mono-substituted phenyl, di-substituted phenyl and mono-substitutednaphthyl, and the ortho substituent is preferably a linear or branchedC₁₋₁₀ alkyl or C₁₋₁₀ alkoxy group. R₃ and R₄ are preferably selectedfrom the group consisting of linear or branched C₁₋₈ alkyl and C₃₋₈cycloalkyl, and even more preferably are methyl or ethyl.

[0044] The aluminum alkyl compound (B) may be triethylaluminum,isobutylaluminum, tri-n-butylaluminum, and linear and cyclicalkylaluminum compounds containing two or more aluminum atoms linked toone another through oxygen or nitrogen atoms or SO₄ or SO₃ groups.Examples of such alkyl aluminum compounds include (C₂H₅)₂Al—O—Al(C₂H₅);(C₂H₅)₂Al—N(C₆H₅)—Al(C₂H₅); (C₂H₅)₂Al—SO₂—Al(C₂H₅);CH₃[(CH₃Al—O—]_(n)Al(CH₃)_(n); and (CH₃Al—O—]_(n). The alkyl aluminumcompound (B) is preferably triethylaluminum.

[0045] The solid catalyst component (C) preferably comprises a titaniumcompound having at least one titanium-halogen bond and an internalelectron donor, both supported on an active magnesium halide.

[0046] The titanium compound, which may be selected from titaniumtetrahalides and titanium alkoxy halides, is supported on the solidmagnesium halide, according to common procedures.

[0047] The titanium compound is preferably TiCl₄.

[0048] The magnesium halide is in anhydrous state, and preferably has awater content of less than 1% by weight. The magnesium halide ispreferably MgCl₂ or MgBr₂, with MgCl₂ being most preferred.

[0049] Those of ordinary skill in this art are well aware how toactivate the magnesium dihalide compound, and to determine its degree ofactivation. More particularly, the active magnesium halides forming thesupport of component (C) are the Mg halides showing in the X-ray powderspectrum of component (C) a broadening of at least 30% of the mostintense diffraction line which appears in the powder spectrum of thecorresponding inactivated magnesium halide having 1 m²/g of surface areaor are the Mg dihalides showing an X-ray powder spectrum in which saidmost intense diffraction line of the inactivated magnesium dihalide isabsent and is replaced by a halo with an intensity peak shifted withrespect to the interplanar distance of the most intense diffraction lineand/or are the Mg dihalides having a surface area greater than 3 m²/g.

[0050] The measurement of the surface area of the Mg halides is made oncomponent (C) after treatment with boiling TiCl₄ for 2 hours. The valuefound is considered as the surface area of the Mg halide.

[0051] The Mg dihalide may be preactivated, may be activated in situduring the titanation, may be formed in situ from a Mg compound, whichis capable of forming Mg dihalide when treated with a suitablehalogen-containing transition metal compound, and then activated, or maybe formed from a Mg dihalide C₁₋₃ alkanol adduct wherein the molar ratioof MgCl₂ to alcohol is 1:1 to 1:3, such as MgCl₂.3ROH where R is a C₁₋₂₀linear or branched alkyl, C₆₋₂₀ aryl or C₅₋₂₀ cycloalkyl.

[0052] Very active forms of Mg dihalides are those showing an X-raypowder spectrum in which the most intense diffraction line appearing inthe spectrum of the corresponding inactivated magnesium halide having 1m²/g of surface area is decreased in relative intensity and broadened toform a halo or are those in which said most intense line is replaced bya halo having its intensity peak shifted with respect to the interplanardistance of this most intense line. Generally, the surface area of theabove forms is higher than 30-40 m²/g and is comprised, in particular,between 100-300 m²/g.

[0053] Active forms are also those derived from the above forms byheat-treatment of component (C) in inert hydrocarbon solvents andshowing in the X-ray spectrum sharp diffraction lines in place of halos.The sharp, most intense line of these forms shows, in any case, abroadening of at least 30% with respect to the corresponding line ofinactivated Mg dihalides having 1 m²/g of surface area.

[0054] The internal electron donor may be selected from alkyl, aryl, andcycloalkyl esters of aromatic acids, especially benzoic acid or phthalicacid and their derivatives, such as ethyl benzoate, n-butyl benzoate,methyl p-toluate, methyl p-methoxybenzoate, and diisobutylphthalate.Alkyl or alkaryl ethers, ketones, mono- or polyamines, aldehydes andphosphorus compounds, such as phosphines and phosphoramides, can also beused as the internal electron donor. The phthalic acid esters are mostpreferred.

[0055] Solid catalyst component (C) can be prepared using techniques andequipments well known to those of ordinary skill in the art. Forexample, the magnesium halide, titanium compound and the internalelectron donor can be milled under conditions where the magnesium halideis active. The milled product is then treated one or more times with anexcess of TiCl₄ at a temperature of from 80° to 135° C. and then washedwith a hydrocarbon such as hexane until all chlorine ions have beenremoved.

[0056] Alternatively, the solid catalyst component (C) may be preparedby first preactivating the magnesium chloride according to knownmethods, reacting it with an excess of TiCl₄ containing the internalelectron donor in solution at a temperature of from 80° to 135° C., andthen washing the solid with a hydrocarbon such as hexane to removeresidual TiCl₄.

[0057] Yet another method for preparing the solid catalyst component (C)includes reacting a MgCl₂nROH adduct (where R is a C₁₋₂₀ linear orbranched alkyl, C₆₋₂₀ aryl or C₅₋₂₀ cycloalkyl), preferably in the formof spheroidal particles, with an excess of TiCl₄ containing the internalelectron donor in solution at a temperature of from 80° to 120° C.,isolating the solid, reacting it once more with TiCl₄ and then washingthe solid with a hydrocarbon, such as hexane, to remove all remainingchlorine ions.

[0058] The molar ratio between the Mg dihalide and the halogenated Ticompound supported thereon is preferably between 1 and 500, while themolar ratio between the halogenated Ti compound and the internalelectron donor supported on the Mg dihalide is preferably between 0. 1and 50. The amount of aluminum alkyl compound (B) employed is generallysuch that an aluminum/titanium ratio is from 1 to 1000.

[0059] The catalyst system comprising an aromatic silane compound (A),an aluminum alkyl compound (B) and a solid catalyst component (C) can beadded to the polymerization reactor by separate means substantiallysimultaneously, regardless of whether the monomer is already in thereactor, or sequentially if the monomer is added to the polymerizationreactor later. It is preferred to premix components (A) and (B), thencontact said premix with component (C) prior to the polymerization forfrom 3 minutes to about 10 minutes at ambient temperature.

[0060] The alpha olefin monomer can be added prior to, with or after theaddition of the catalyst to the polymerization reactor. It is preferredto add it after the addition of the catalyst.

[0061] Another object of the instant invention is a process for thepolymerization of alpha-olefins carried out in the presence of thecatalyst system as described above.

[0062] The polymerization reactions can be done in slurry, liquid or gasphase processes, or in a combination of liquid and gas phase processesusing separate reactors, all of which can be done either by batch orcontinuously.

[0063] The polymerization is generally carried out at a temperature offrom 0 to 150° C., and preferably from 40 to 90° C.; the polymerizationmay be carried out at atmospheric pressure or at higher pressures,preferably from 100 to 10,000 kPa, and more preferably from 200 to 8,000kPa.

[0064] Chain terminating agents, such as hydrogen, can be added asneeded to reduce the molecular weight of the polymer, according tomethods well known in the state of the art.

[0065] The catalysts may be precontacted with small quantities of olefinmonomer (prepolymerization), maintaining the catalyst in suspension in ahydrocarbon solvent and polymerizing at a temperature of 60° C. or belowfor a time sufficient to produce a quantity of polymer from 0.5 to 3times the weight of the solid catalyst component.

[0066] This prepolymerization also can be done in liquid or gaseousmonomer to produce, in this case, a quantity of polymer up to 1000 timesthe catalyst component weight.

[0067] Suitable alpha-olefins which can be polymerized by this inventioninclude olefins of the formula CH₂═CHR, where R is H or C₁₋₂₀ straightor branched alkyl, such as ethylene, propylene, butene-1, pentene-1,4-methylpentene-1 and octene-1.

[0068] The aromatic silane compounds of the present invention, as wellas the polymerization catalyst systems containing them, enable theproduction of propylene polymers, and in particular propylenehomopolymer having a stereoblock content of from about 7 to about 25%,and preferably from 12 to 20%, by changing the ortho substituent on thearomatic ring of the silane themselves.

[0069] Propylene polymers prepared using the external electron donors ofthe present invention may be manufactured into films using conventionalapparatus and techniques well known to those of ordinary skill in thepolyolefin art.

EXAMPLES

[0070] The examples below illustrate specific embodiments of theinvention, and are not intended to limit the scope of the invention inany manner whatsoever.

[0071] General procedures and characterizations

[0072] Purity of all reagents was confirmed by either chromatographic orspectrophotometric analysis. Where appropriate, reagents were purifiedprior to use. All nonaqueous reactions were performed under anatmosphere of dry nitrogen or argon using glassware that was dried undervacuum while heated. Air and moisture sensitive solutions weretransferred via syringe or stainless steel cannula. Reported boilingpoints and melting points were uncorrected.

[0073] No spectra were recorded on a Varian Unity 300 spectrometeroperating at 300 MHz and are referenced internally to eithertetramethylsilane or residual proton impurities. Data for ¹H arereported as follows: chemical shift, (δ, ppm), multiplicity (s-singlet;d-doublet; t-triplet; q-quartet, qn-quintet; m-multiplet), integration.Data for ¹³C NMR are reported in terms of chemical shift (δ, ppm).

[0074] Infrared spectra were reported on a BioRad FT430 series mid-IRspectrometer using KBr plates and are reported in terms of frequency ofabsorption (v, cm⁻¹).

[0075] Gas chromatographic analyses were conducted using a HewlettPackard model 6890 chromatograph using flame ionization detection(“FID”) coupled to a model HP6890 integrator. In a typical analysis 1.0μL was injected into a 250° C. injector (50:1 split ratio; 10 psi columnhead pressure, 106 mL/min split flow; 111 mL/min total flow). Helium wasused as a carrier gas through an Alltech Heliflex AT-1 column (30 m×0.32mm×0.3 μm). The initial temperature was held at 50° C. for two minutesthen increased at 10° C./min to a final temperature of 300° C. The FIDdetector was held at 300° C. (40 mL/min H₂; 400 mL/min air; constantmake-up mode using 30 mL/min He).

[0076] Two GC/MS systems were used. One system was a Hewlett Packardmodel 5890 GC coupled to a Hewlett Packard model 5970 mass selectivedetector. In a typical analysis, 2.0 μL of sample was injected into a290° C. splitless injection port. Helium was used as the carrier gasthrough an HP-1 column (Hewlett Packard, 25 m×0.33 mm×0.2 μm). Theinitial temperature was held at 75° C. for four minutes. The column waswarmed at 10° C./min. Mass acquisition was 10-800 AMU. The spectra arereported as m/z (relative abundance).

[0077] The second GC/MS system was a Hewlett Packard model 6890 GCcoupled to a Hewlett Packard model 5973 mass selective detector. In atypical analysis, 1.0 μL of sample was injected into a 290° C.split/splitless injection port. Helium was used as the carrier gasthrough an BP-5 column (Hewlett Packard, 30 m×0.25 mm×0.25 μm). Theinitial temperature was held at 50° C. for four minutes. The column waswarmed at 10° C./min. Mass acquisition was 10-800 AMU. The spectra arereported as m/z (relative abundance).

[0078] Temperature Rising Elution Fractionation technique (TREF) wasused to analyze the crystalline structure of the polymers. The techniqueuses xylene as a solvent to dissolve the polymer crystal structure anddetermines the dissolved amount as the temperature is raised above roomtemperature up to a point where all of the polymer is dissolved. Theportion dissolved at room temperature is designated as atactic; theportion dissolved between room temperature and 100° C. is designated asstereoblock, and the remaining portion above 100° C. is calledisotactic.

Synthesis of Aromatic Silane Compounds Example 1 Synthesis of(2-ethylphenyl)-propyl-dimethoxysilane

[0079] A 500 mL round bottomed flask was charged with magnesium turnings(2.73 g, 112 mmol, Aldrich) and ether (300 mL, Aldrich).Bromo-2-ethylbenzene (18.7 mL, 135 mmol, Aldrich) was added over 30minutes. The reaction stirred for three hours at room temperature andbecame dark brown in color. The contents were refluxed for one hour.

[0080] The contents were cooled to 0° C. and propyl-trimethoxysilane(19.8 nL, 112 mmol) was added over 25 minutes. The reaction was stirredat room temperature overnight (18 hours) during which time a whiteprecipitate formed. The contents were poured into water (500 mL), thelayers separated and the product extracted into ether (3×150 mL). Thecombined organic portions were dried (MgSO₄), filtered and the solventremoved via rotary evaporation providing 28.9 g crude material.Distillation under reduced pressure (b.p. 89° C., 0.7 mm Hg) produced(2-ethylphenyl)-propyl-dimethoxysilane (12.2 g, 51.3 mmol, 45.8% yield);C₁₃H₂₂SiO₂:(Mw=238.40); ¹H NMR (CDCl₃)δ7.7(m, 1H), 7.4-7.1 (m, 3H), 3.5(s, 6H), 2.8 (q, 2H), 1.4 (m, 2H), 1.2 (t, 3H), 0.9-0.8 (m, 5H); ¹³CNMR(CDC₃)δ150.5, 135.8, 131.3, 130.3, 128.0, 124.9, 50.3, 28.6, 17.7, 16.3,15.9, 0.1; IR (capillary film) v 3054, 2966, 2874, 2836, 1590, 1460,1192, 1128, 1104, 998, 809, 752; MS m/z (relative abundance) 238 (6.5),195 (100), 163 (58.8), 133 (28.6), 105 (10.7), 91 (14.9), 59 (23.7).

Comparative Example 1 Synthesis of (phenyl)-propyl-dimethoxysilane

[0081] A 500 mL round bottomed flask was charged withpropyl-trimethoxysilane (19.3 mL, 1.10×10⁻¹ mole, Hüls) and ether (250mL, Aldrich). A pressure equalizing addition funnel was charged withphenylmagnesium bromide (33.3 mL of a 3M solution in ether, 99.9 mmol,Aldrich) and ether (50 mL). The contents of the addition funnel wereadded into the silane over a 20 minute period (exotherm). A whiteprecipitate formed. The reaction was stirred for two hours at roomtemperature then poured into 0.2N HCl (300 mL). The layers wereseparated, the product extracted into ether (2×250 mL), dried (MgSO₄),and filtered. The solvent was removed via rotary evaporation resultingin 23.5 grams of crude material. Distillation under reduced pressure(b.p. 71° C., 0.6 mm Hg) provided phenyl-propyl-dimethoxysilane (18.5 g,88.0 mmol, 88% yield); C₁₁H₁₈SiO₂ (mw=210.34); ¹H NMR (CDCl₃)δ7.7 (m,2H), 7.4 (m, 3H), 3.6 (s, 6H), 1.4 (m, 2H), 1.0 (t, 3H), 0.9 (t, 2H);¹³C NMR (CDCl₃)δ134.3, 133.3, 130.1, 127.9, 50.6, 17.9, 16.3, 14.8; MSm/z (relative abundance) 210 (2), 167 (100), 137 (33), 107 (17), 91(17), 59 (10).

Example 2 Synthesis of (2-ethylphenyl)-3-methylbutyl-dimethoxysilane

[0082] A 1000 mL round bottomed flask was charged with magnesiumturnings (1.97 g, 81.0 mmol, Aldrich) and ether (500 mL, Aldrich).Bromo-2-ethylbenzene (14.0 mL, 101 mmol, Aldrich) was added over 30minutes. The reaction stirred for three hours at room temperature andbecame dark brown in color. The contents were refluxed for one hour. Thecontents were cooled to 0° C. and isoamyl-trimethoxysilane (15.9 g, 82.8mmol, previously prepared by reaction between isoamyl magnesiumbromideand tetramethylortho-silicate) was added over 25 minutes. The reactionwas stirred at room temperature overnight (18 hours) during which time awhite precipitate formed. The contents were poured into water (500 mnL),the layers separated and the product extracted into ether (3×150 mL).The combined organic portions were dried (MgSO₄), filtered and thesolvent removed via rotary evaporation providing 29.6 g crude material.Distillation under reduced pressure (b.p. 109° C., 1.1 mm Hg) produced(2-ethylphenyl)-3-methylbutyl-dimethoxysilane (7.68 g, 28.8 mmol, 35.6%yield); C₁₅H₂₆SiO₂ (Mw=266.45); ¹H NMR (CDCl₃)δ7.7 (m, 1H), 7.3 (m, 1H),7.2 (m, 2H), 3.5 (s, 6H), 2.8 (q, 2H), 1.4 (m, 1H), 1.2(m, 5H), 0.8(m,8H); ¹³C NMR (CDCl₃)δ150.5, 135.9, 131.2, 130.3, 128.0, 124.9, 50.3,31.5, 30.7, 28.6, 21.9, 16.1, 10.9; IR(capillary film) v 3054, 2974,1590, 1467, 1370, 1200, 1118, 1023, 936, 874 803, MS m/z (relativeabundance) 266 (0.02), 195 (100), 163 (59.1), 160 (28.8), 133 (25.5),105 (11.2), 91 (12.3), 59 (18.4).

Comparative Example 2

[0083] (Phenyl)-3-methylbutyl-dimethoxysilane was synthesized accordingto the procedure reported in Example 2, but using bromo-benzene insteadof bromo-2-ethylbenzene.

Example 3 Synthesis of (2,4-dimethoxyphenyl)-propyl-dimethoxysilane

[0084] A 500 mL round bottomed flask was charged with hexane (200 mL,Aldrich) and bromo-2,4-dimethoxybenzene (12.2 g, 56.0 mmol, Aldrich).The contents were cooled to 0° C. and n-butyl lithium (34.7 mL of a 1.6Msolution in hexanes, 55.5 mmol, Aldrich) was added over 15 minutes(white precipitate). The contents were stirred at room temperature forninety (90) minutes. The solution was added, via cannula, into a 1000 mLround bottomed flask containing hexane (300 nL, Aldrich) andpropyl-trimethoxysilane (9.8 mL, 56 mmol). The reaction was stirred atroom temperature overnight (18 hours). Ethanol (10 mL, Aldrich) wasadded to quench residual base. The contents were poured into 0.2N HCl(250 mL). The layers were separated and the product extracted into ether(2×150 nL). The combined organic portions were dried (MgSO4), filtered,and the solvent removed via rotary evaporation (16.2 g crude).Distillation under reduced pressure (b.p. 115° C., 0.04 mm Hg) provided2,4-dimethoxyphenyl-propyl-dimethoxysilane (9.13 g, 33.8 mmol, 61%yield); C₁₃H₂₂O₄Si (Mw=270.40); ¹H NMR (CDCl₃)δ7.5 (d, 1H), 6.5 (m, 1H),6.4 (d, 1H), 3.8 (s, 3H), 3.8 (s, 3H), 3.5 (s,6H), 1.4 (m, 2H), 0.9 (t,3H), 0.8 (t, 2H); ¹³C NMR (CDCl₃)δ165.8, 163.2, 137.6, 112.7, 104.6,97.5, 55.0, 54.9, 50.4, 17.7, 16.2, 15.4; IR (capillary film) v 2950,2836, 1596, 1571, 1460, 1299, 1206, 1154, 1089, 1036; MS rn/z (relativeabundance) 270 (11.1), 227 (45.6), 197 (100), 167 (24.4), 137 (10.9),121 (22.6), 91 (9.9), 59 (18.4).

Comparative Example 3

[0085] (4-Methoxyphenyl)-propyl-dimethoxysilane was synthesizedaccording to the procedure reported in Example 3, but usingbromo-4-dimethoxybenzene instead of bromo-2,4-dimethoxybenzene.

Example 4

[0086] (2-Methoxynaphthyl)-propyl-dimethoxysilane was synthesizedaccording to the procedure reported in Example 3, but usingbromo-2-methoxynaphthalene instead of bromo-2,4-dimethoxybenzene.

Example 5 Synthesis of (2,6-dimethylphenyl)-propyl-dimethoxysilane

[0087] A 500 mL round bottomed flask was charged with magnesium powder(2.1 g, 86 mmol, Aldrich) and ether (250 mL, Aldrich). 2-Bromo-m-xylene(9.0 mL, 68 mmol, Aldrich) was added over a 25 minute period. Thecontents were refluxed overnight (18 hours). The brown solution wascooled to room temperature and propyl-trimethoxysilane (17.8 mL, 101mmol) was added over 20 minutes. A white precipitate formed. Thecontents were stirred at room temperature overnight (18 hours). Thereaction was poured into 0.2N aqueous HCI (500 mL), the layers wereseparated and the product extracted into ether (3×150 mL). The combinedorganic portions were dried (MgSO4), filtered, and the solvent removedvia rotary evaporation (13.5 g crude). Distillation under reducedpressure (b.p. 57° C., 0.04 mm Hg) provided(2,6-dimethylphenyl)-propyl-dimethoxysilane (6.8 g, 28 mmol, 41% yield);C₁₃H₂₂SiO₂ (Mw=238.40);¹H NMR (CDCl₃)δ7.2 (t, 1H), 7.0 (d, 2H), 3.6 (s,6H), 2.5 (s, 6H), 1.4 (m, 2H), 1.0 (t, 3H), 0.9 (t, 2H); ¹³C NMR(CDCl₃)δ145.2, 131.0, 129.6, 128.0, 49.8, 23.4, 17.9, 16.7, 16.3; MSnl/z (relative abundance) 238 (8), 195 (100), 165 (22), 133 (12), 119(10), 105 (13), 91 (9), 59 (16).

Comparative Examples 4-6

[0088] The silane compounds (4-methyl-phenyl)-propyl-dimethoxysilane, (4-propyl-phenyl)-propyl-dimethoxysilane and(4-chloro-phenyl)-propyl-dimethoxysilane were synthesized according tothe procedure reported in Example 2, but using respectivelybromo4-methyl-benzene, bromo-4-propyl-benzene and bromo-4-chloro-benzeneinstead of bromo-2-ethylbenzene.

Example 6 Synthesis of(2-ethyl-phenyl)-3,3-dimethylbutyl-dimethoxysilane

[0089] Under an atmosphere of dry nitrogen a magnetically stirredsuspension of anhydrous tetrahydrofuran (Aldrich, 300 mL) and magnesiumturnings (Aldrich, 1.2 g, 49 mmol) was treated dropwise at roomtemperature with 1-bromo-2-ethylbenzene (Aldrich, 6.1 mL, 44 mmol).After 10 minutes the reaction mixture began to reflux mildly. After theaddition was complete the reaction mixture was heated to refluxovernight (18 h). A separate flask was flushed with dry nitrogen andthen charged with anhydrous tetrahydrofuran (Aldrich, 100 mL) and3,3-dimethylbutyl-trimethoxysilane (Huls, 11.4 mL, 49 mmol). TheGrignard solution was cooled to room temperature and then added to thesilane solution at room temperature via stainless steel cannula. Thereaction mixture stirred at room temperature overnight (18 h). Ethylalcohol (Aldrich, 5 mL) was added to quench any remaining Grignard. Thereaction mixture was concentrated on a rotary evaporator and distilledin vacuum to give 3.7 g (30%) of the title compound as a colorless oil(b.p. 107-108° C. at 0.5 mm Hg, 99% GC-purity): C₁₆H₂₈O₂Si (Mw=280).

Propylene Polymerization

[0090] Preparation of the solid catalyst component

[0091] Into a 500 mL four-necked round flask, purged with nitrogen, 250mL of TiCl₄ were introduced at 0° C. While stirring, 10.0 g ofmicrospheroidal MgCl₂.2.8C₂H₅OH (prepared according to the methoddescribed in example 2 of U.S. Pat. No. 4,399,054, but operating at 3000rpm instead of 10000 rpm) and 7.4 mmol of diisobutylphthalate wereadded. The temperature was raised to 100° C. and maintained for 120minutes. Then the stirring was discontinued, the solid product wasallowed to settle and the supernatant liquid was siphoned off. 250 mL offresh TiCl₄ were then added. The mixture was reacted at 120° C. for 60min and, then, the supernatant liquid was siphoned off. The solid waswashed six times with anhydrous hexane (6×100 mL) at 60° C.

[0092] Polymerization procedure

[0093] A polymerization reactor was heated to 70° C. and purged with aslow argon flow for 1 hour; its pressure was then raised to 100 psigwith argon, at 70° C., and the reactor was vented. This procedure wasrepeated 4 more times. The reactor was then cooled to 30° C.

[0094] Separately, into an argon purged addition funnel, the followingwere introduced in the order they are listed: 75 mL of hexane, 4.47 mLof a 1.5M solution of triethylaluminum (TEAL) (0.764 g, 6.70 mmol) inhexane, about 0.340 mmol of an aromatic silane compound, as indicated inthe following examples (so that the molar ratio of TEAL:organosilaneequaled approximately 20:1), and the obtained mixture was allowed tostand for 5 minutes. Of this mixture, 35 mL were added to a flask. Then0.0129 g of the solid catalyst component, prepared as described above,were added to the flask and mixed by swirling for a period of fiveminutes. The catalytic complex so obtained was introduced, under anargon purge, into the above polymerization reactor at room temperature.The remaining hexane/TEAL/silane solution was then drained from theaddition funnel to the flask, the flask was swirled and drained into thereactor and the injection valve was closed. The polymerization reactorwas slowly charged with 2.2 L of liquid propylene, under stirring, and0.25 mole percent of H₂ were introduced. The reactor was then heated to70° C. and the polymerization was carried out for about 2 hours, atconstant temperature and pressure. After about 2 hours under stirring,the polymerization was stopped and the remaining propylene was slowlyvented. The reactor was heated to 80° C., purged with argon for 10minutes and then cooled to room temperature and opened. The polymer wasremoved and dried in a vacuum oven at 80° C., for 1 hour.

Examples 7-11 and Comparative Examples 7-12

[0095] In Examples 7-11, polypropylene polymers were prepared inaccordance with the polymerization procedure reported above, using theorganosilane compounds synthesized in the previous examples as theexternal electron donor in otherwise identical catalyst systems.

[0096] In Comparative Examples 7-12, the same polymerization procedurewas cared out by using aromatic silane compounds wherein the aromaticring does not bear any substituents in the ortho position.

[0097] The aromatic silane compounds used in the polymerization, as wellas the stereoblock content of the resultant polymer and thepolymerization yields are reported in Table 1. TABLE 1 Stereoblock YieldExample Silane compound (% wt.) (kg/g_(cat)) Example 7(2-ethylphenyl)-propyl- 13.3 45.2 dimethoxysilane Comp. Ex. 7phenyl-propyl-dimethoxysilane 8.0 46.7 Example 8(2-ethylphenyl)-3-methylbutyl- 19.7 40.1 dimethoxysilane Comp. Ex. 8phenyl-3-methylbutyl- 19.0 30.2 dimethoxysilane Example 9 (2,4-dimethoxyphenyl)-propyl- 14.9 24.3 dimethoxysilane Comp. Ex. 9(4-methoxyphenyl)-propyl- 10.9 28.5 dimethoxysilane Example 10(2-methoxynaphthyl)-propyl- 21.4 20.8 dimethoxysilane Example 11(2-ethyl-phenyl)-3, 3- 20.4 34.2 dimethylbutyl-dimethoxysilane Comp. Ex.10 (4-methylphenyl)-propyl- 10.7 45.5 dimethoxysilane Comp. Ex. 11(4-propylphenyl)-propyl- 9.8 43.1 dimethoxysilane Comp. Ex. 12(4-chlorophenyl)-propyl- 7.5 42.9 dimethoxysilane

[0098] The data reported in the above table show that the propylenepolymers obtained with the aromatic silane compounds of the presentinvention, having a substituent in the ortho position of the aromaticring, have unexpectedly a higher stereoblock content, with respect tothe polypropylenes obtained with analogous unsubstituted compounds orwith compounds bearing a substituent in a position other than ortho onthe aromatic ring.

[0099] Other features, advantages and embodiments of the inventiondisclosed herein will be readily apparent to those exercising ordinaryskill after reading the foregoing disclosures. In this regard, whilespecific embodiments of the invention have been described inconsiderable detail, variations and modifications of these embodimentscan be effected without departing from the spirit and scope of theinvention as described and claimed.

1. An aromatic silane compound having formula (I):

wherein R₁ is selected from the group consisting of linear or branchedC₁₋₂₆ alkyl, C₂₋₂₆ alkenyl, C₁₋₂₆ alkoxy, C₂₋₂₆ alkoxyalkyl, C₇₋₂₆arylalkyl, C₃₋₂₆ cycloalkyl and C₄₋₂₆ cycloalkoxy groups, optionallycontaining one or more halogen atoms; R₂ is an aromatic ring having atleast one substituent in the ortho position selected from C₁₋₁₀hydrocarbon groups; and R₃ and R₄, the same or different from eachother, are selected from the group consisting of linear or branchedC₁₋₁₀ alkyl and C₃₋₁₀ cycloalkyl groups:
 2. The aromatic silane compoundof claim 1, wherein R₁ is selected from the group consisting of linearor branched C₁₋₁₈ alkyl and C₃₋₁₈ cycloalkyl groups.
 3. The aromaticsilane compound of claim 2, wherein R₁ is selected from the groupconsisting of linear C₁₋₅ alkyl and branched C₃₋₈ alkyl groups.
 4. Thearomatic silane compound of claim 1, wherein R₂ is selected from thegroup consisting of mono-substituted phenyl, di-substituted phenyl andmono-substituted naphthyl.
 5. The aromatic silane compound of claim 1,wherein R₃ and R₄ are selected from the group consisting of linear orbranched C₁₋₈ alkyl and C₃₋₈ cycloalkyl groups.
 6. The aromatic silanecompound of claim 5, wherein R₃ and R₄ are methyl or ethyl.
 7. Acatalyst system for the polymerization of olefins comprising: (A) anaromatic silane compound having formula (I):

wherein R₁ is selected from the group consisting of linear or branchedC₁₋₂₆ alkyl, C₂₋₂₆ alkenyl, C₁₋₂₆ alkoxy, C₂₋₂₆ alkoxyalkyl, C₇₋₂₆arylalkyl, C₃₋₂₆ cycloalkyl and C₄₋₂₆ cycloalkoxy groups, optionallycontaining one or more halogen atoms; R₂ is an aromatic ring having atleast one substituent in the ortho position; and R₃ and R₄, the same ordifferent from each other, are selected from the group consisting oflinear or branched C₁₋₁₀ alkyl and C₃₋₁₀ cycloalkyl groups; (B) analuminum alkyl compound; and (C) a solid catalyst component comprisingMg, Ti, halogen and an electron donor compound.
 8. The catalyst systemof claim 7 wherein, in said aromatic silane compound (A), R₁ is selectedfrom the group consisting of linear or branched C₁₋₁₈ alkyl, C₁₋₁₈alkoxyl and C₃₋₁₈ cycloalkyl groups.
 9. The catalyst system of claim 8,wherein R₁ is selected from the group consisting of linear C₁₋₅ alkyland branched C₃₋₈ alkyl groups.
 10. The catalyst system of claim 7wherein, in said aromatic silane compound (A), R₂ is selected from thegroup consisting of mono-substituted phenyl, di-substituted phenyl andmono-substituted naphthyl, and said substituent in the ortho position isselected from the group consisting of linear or branched C₁₋₁₀ alkyl andC₁₋₁₀ alkoxy groups.
 11. The catalyst system of claim 7 wherein, in saidaromatic silane compound (A), R₃ and R₄ are selected from the groupconsisting of linear or branched C₁₋₈ alkyl and C₃₋₈ cycloalkyl groups.12. The catalyst system of claim 11, wherein R₃ and R₄ are methyl orethyl.
 13. The catalyst system of claim 7, wherein said solid component(C) comprises a titanium compound having at least one titanium-halogenbond and an internal electron donor, both supported on an activemagnesium halide.
 14. The catalyst system of claim 13, wherein saidsolid component (C) comprises the reaction product of titaniumtetrachloride, active magnesium chloride and an internal electron donor.15. A process for the polymerization of alpha-olefins comprisingpolymerizing propylene in the presence of the catalyst system asdescribed in claim 7, to produce a polyolefin having a stereoblockcontent of from about 7 to about 25%.